You are in: eMedicine Specialties > Orthopedic Surgery > KNEE Complications of Total Knee ArthroplastyArticle Last Updated: Jun 24, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 5
  Author: Mervyn J Cross, MBBS, FRACS, Director of the Australian Institute of Musculoskeletal Research, Department of Orthopedic Surgery, North Sydney Orthopedic/Sports Medicine Center, Crows Nest, Australia Mervyn J Cross is a member of the following medical societies: American Orthopaedic Society for Sports Medicine, Australasian College of Sports Physicians, Australian Association of Surgeons, Australian Medical Association, Australian Orthopaedic Association, Hughston Society, and Royal Australasian College of Surgeons Editors: Phillip J Marone, MD, Clinical Professor, Department of Orthopedic Surgery, Jefferson Medical College; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Thomas M DeBerardino, MD, Director, John A Feagin, Jr, Sports Medicine Fellowship at West Point, Associate Professor of Orthopedic Surgery, Uniformed Services University of the Health Sciences and Keller Army Community Hospital; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Carlos J Lavernia, MD, FAAOS, Adjunct Clinical Professor, Department of Orthopedic Surgery, University of Miami School of Medicine; Medical Director, Orthopedic Institute at Mercy Hospital Author and Editor Disclosure Synonyms and related keywords: total knee replacement, knee arthritis, osteoarthritis, deep venous thrombosis, deep vein thrombosis, DVT, arthroplasty-associated infections, knee infection, arthroplasty component failure, unicompartmental knee arthroplasty, patellar tendon rupture, periprosthetic fractures, immune response to implants, metallic alloys COMPLICATIONSSection 2 of 5
  Total knee replacement has become an acceptable method of treating severe arthritis of the knee. The operative procedure must be performed with precise skill and accuracy. Meticulous alignment of the prosthetic components can reduce many of the complications. Fine attention to general operating technique with adroit handling of tissues and efficient teamwork can reduce operating time to a minimum and thus avoid exposing the wound for an inordinate amount of time. An experienced, efficient technique also aids in preventing deep venous thrombosis and unnecessary scarring and decreases many of the complications that are associated with total knee arthroplasty. An implanted knee with excellent insertion can be seen in Image 1. Complications can be classified as those specific to the operation, general complications of the anesthetic (perioperative complications), and other medical complications (postoperative complications). Perioperative complications include blood loss, infection, early hemorrhage and wound breakdown, intraoperative fractures, and anesthetic problems, as well as cardiovascular, respiratory, renal, electrolyte, and other medical problems.1 Deep venous thrombosis is a major danger, particularly if it embolizes to the lung. Precautions are necessary with early mobilization, thromboembolic disease stockings, foot pumps, and anticoagulant therapy. Low-molecular-weight heparin is the drug of choice for prophylaxis. Administering warfarin (Coumadin) 10 mg the night prior to surgery, followed by a daily dose that keeps the international normalized ratio of 1.5-2 for 8 weeks, is also satisfactory. Asymptomatic deep vein thrombosis has been reported in up to 50-70% of patients who receive total knee arthroplasty. Postoperative ultrasonography or venography can reveal the presence of thrombi quite successfully. Infection is rare following total knee arthroplasty. It occurs in 1-2.5% of cases. In the early perioperative stages, it should be diagnosed and treated on an urgent basis. Prophylactic antibiotics are used routinely for the first 24 hours. Neurovascular complications are rare in total knee arthroplasty. The lateral popliteal nerve may be injured in severe valgus deformity. Tourniquet paralysis may also occur as a rare problem. Major vessel injury may occur in revision procedures or in the rare case in which anatomy is abnormal.2, 3 LONG-TERM PROBLEMSSection 3 of 5
Major long-term problems that are associated with total knee arthroplasty are late infection, wearing of the bearings, and loosening of the prosthesis.4 Periprosthetic fracture and arthrofibrosis are other problems that may occur but are less common. Research is progressing on the wear properties of polyethylene (ultra–high-molecular-weight polyethylene). The coefficient of friction between polyethylene and cobalt-chromium alloy (commonly used for femoral components) has been reported to be between 0.03 and 0.16, with excellent wear rates. The shape and congruency of the bearing surface is important, with respect to contact of the metal component on the polyethylene. The mobile bearing insert (as opposed to a fixed bearing) is under continuing research, with the focus directed on the contact between these surfaces, such that research efforts aim at achieving low contact stresses to decrease wear and further increase range of movement. There is much more contact area in mobile bearing systems; this is seen by some to be a disadvantage, as there is more area to wear. Mobile bearings have significantly reduced upper and lower surface stresses, as compared with fixed-bearing components. Unconstrained mobile bearings have a theoretical advantage, when compared with semiconstrained mobile bearings (which allow rotation or translation), as they avoid higher shear stresses, but they also have an increased risk of subluxation. Low friction is the aim in all prosthesis design. Therefore, opportunities for improvement include developing finer polishing techniques and better interface materials. An example of advanced polyethylene wear can be seen in Image 2. Ceramics are now commonly used in hip prostheses but rarely in the knee. Better grades and design of ceramics will eventually appear. Instrumentation has improved prosthesis implantation techniques so that malalignment and incorrect insertion have been reduced to a minimum. Computer-assisted surgery is under research, and many believe that this will decrease the incidence of less-than-satisfactory implantation.5, 6, 7, 8 When embarking on a surgical procedure that has a finite life span, such as a joint replacement, it is important to keep the next revision procedure in mind.9 It is essential in the primary procedure to preserve bone, to not invade the medulla if possible (an advantage of using a stemless prosthesis), and to preserve soft tissues, especially ligaments. Osteolysis is a major problem with polyethylene and metal wear fragments. The pathology consists of a significant synovitis caused by wear particles in the synovial cavity. Due to the Pascal principle, major forces are produced and transmitted throughout the synovial fluid. The wear particles are forced along the lines of least resistance, and the inflamed synovium tracks down the vascular bony foramina around the joint.12 Severe osteolysis can also occur in pigmented villonodular synovitis and in patients with hemophilia.13 Preoperative assessment and knowledge of previous injuries and operations are important. Image 4 shows a previous infection of the tibia with osteomyelitis and tethering of the skin to the bone. Skin viability had to be assessed during the procedure to ensure that there would be no breakdown in the postoperative period. Dislocation of a total knee arthroplasty can be seen in Image 5, which demonstrates poor soft-tissue balancing. Inadequate spacer insertion, poor ligament balancing, excessive bone resection, and/or malrotation of the prosthesis can cause this to occur. Many total knee replacements are inserted in less-than-ideal ways. Image 6 shows a case with many faults that ultimately led to excessive wear and osteolysis around the stem. It shows the femoral component inserted in flexion and large cysts behind the cemented tibial component. When these technical abnormalities are present in a total knee replacement, they often result in premature failure of the prosthesis and require early revision. Complications associated with the patellar component are another cause of failure in a total knee arthroplasty. Potential complications involving the patella include patella tendon avulsion (often associated with a previous high tibial osteotomy), patellofemoral instability due to inadequate soft-tissue balancing, and component failure caused by factors such as a metal-backed component, recurrent instability, loosening, or fracture.14 Patella clunk is associated with posterior cruciate-sacrificing prosthesis designs in which the peg hits the patella. Fixation of components with or without cement is still debated widely. Studies comparing both methods have revealed little, if any, differences.15 Bioactive coatings such as hydroxyapatite have been used to enhance uncemented fixation, with favorable medium- to long-term results. Prosthetic loosening is the most common cause of long-term failure in total knee arthroplasty, due to osteolysis from wear-particle synovitis. Infection is a major disaster in any joint replacement. It is important to diagnose early and treat on an urgent basis. The differential diagnosis in the early perioperative period is between superficial and deep infection. Blood tests, such as erythrocyte sedimentation rate and C-reactive protein, are not helpful, as the trauma of surgery can affect these. Elevated temperature is an indication, and the presence of a red, inflamed joint confirms the diagnosis. Saving the prosthesis is possible if early exploration and thorough synovectomy are performed. The chances of preserving the prosthesis are better if it is uncemented. In late infections, complete removal of the prostheses is indicated, with removal of all components and cement. Measurements of erythrocyte sedimentation rate and C-reactive protein are important for the diagnosis of a chronic infection. Usually, revision of the components is required. A 2-stage revision is best. A postoperative temporary (first-stage) insert can be seen in Image 7. It is important to excise all infected tissue, which requires a complete synovectomy and thorough washout with at least 10 liters of isotonic sodium chloride solution. The differential diagnosis of chronic pain in the late stage includes aseptic loosening, arthrofibrosis, sympathetic dystrophy, and, possibly, referred pain from the hip or spine. Arthrolysis may be of benefit with severe arthrofibrosis. Periprosthetic fracture is a rare complication (1-5%) and is usually the result of trauma. Therefore, it is treated on an individual basis, depending on the site and type of fracture.16 Other causes include notching of the femoral component and osteoporosis.17 It may be necessary in some cases to insert a large-stem prosthesis. Femoral fracture is the most common type of fracture and usually occurs in the supracondylar region. For excellent patient education resources, visit eMedicine's Breaks, Fractures, and Dislocations Center and Circulatory Problems Center. Also, see eMedicine's patient education articles Knee Joint Replacement and Blood Clot in the Legs. MULTIMEDIASection 4 of 5
REFERENCESSection 5 of 5
Complications of Total Knee Arthroplasty excerpt Article Last Updated: Jun 24, 2008 | |||||||||||||||||||||||||||||||||||||||||||||||||
